Chain stitch sewing machine

ABSTRACT

Apparatus for producing a continuous chain stitch on a sewing machine having one or more needles with minimum or negligible seam stretching in which one or more rows of serrated teeth in a feed dog are foreshortened and a pressure pad mounted on a presser foot guides a chain stitch and fabric on a throat plate continuously and prevents thread feedback or reverse thread displacement from its directed path of travel.

United States Patent Fulp 1 Dec. 2, 1975 [54] CHAIN STITCH SEWING MACHINE 2,882,846 4/1959 Coates 112/216 3,233,570 2/1966 James 112/216 [751 Inventor: James Full Summerfield- 3,476,065 11/1969 Marforio 112/197 [73] Assignee: Blue Bell, Inc., Greensboro, NC. [22] Filed Dec 3 1974 Primary Examiner-Geo. V. Larkin 21 A 1. No.: 529 238 1 pp 57 ABSTRACT [52] us. Cl U 112/197, 1 Hum Apparatus for producing a continuous chain stitch on [51] Int Cl 2 DOSB 27/02' a sewing machine having one or more needles with [58] i 260 235 minimum or negligible seam stretching in which one 1 6 or more rows of serrated teeth in a feed dog are foreshortened and a pressure pad mounted on a presser [56] References Cited foot guidesla chgin stitch 31:1 fagrtic 3g althroat plate contmuousy an prevents t rea ee ac or reverse UNITED STATES PATENTS thread displacement from its directed path of travel. 2,307,513 l/l943 Vessler 112/216 2,427,467 9/1947 Loiselle 112/216 5 Claims, 3 Drawing Figures- US. Patent I Dec. 2, 1 975 FIG.3

CHAIN STITCH SEWING MACHINE BACKGROUND AND OBJECTIVES OF THE INVENTION The formation of a continuous chain stitch on certain types of industrial sewing machines is well known and is used rather widely in connection with overedge sewing machines and other sewing machines in which a continuous chain connects a series of garments or portions of garments including such articles as stockings or socks. The connecting chain of stitches between articles may be severed either manually or automatically by means of a scissors, knife or hot wire depending upon the specific application with excess threads in the chain being removed pneumatically, in an automatic operation, to a remote collection chamber.

It has been found in the manufacture of certain seams on some industrial sewing machines for garments in which there is a fell seam that for some'fabrics the operator is required to stretch or apply tension to the fabric as it is being fed to the sewing instrumentalities in order to provide a finished seam that'is uniform, has some stretchability, and does not have objectionable puckering or boardiness. It is desirable to maintain as nearly as possible the main fabric characteristics in the seam despite sewing several plies of fabric together in an overlapping relationship. A properly formed seam is referred to sometimes as a sanforized seam as it exhibits substantially the same fabric characteristics as the main body of the fabric.

Presently a sewing machine operator is unable to chain-off by feeding one garment or section of a garment to certain types of sewing machines and position another garment or section of a garment immediately following the trailing edge of the first garment or section of a garment by continuously sewing. The operator on such industrial sewing machines including Union Special sewing machines Styles 56400; 56500; and 56900, among others including Singer machines, are not provided with any suitable means for enabling an operator to chain-off. The operator must stop sewing after completion of the seam being sewn in the preceding garment or section of a garment and then place the succeeding garment seam to be sewn under the presser foot thereby breaking the continuous operation and necessitating the application of tension to the seam to be sewn by the operator. The succeeding garment or section of a garment to be sewn must be placed under the presser foot without a linking of the chain stitch between the trailing end of one unit being connected in any manner to the leading end of the next unit.

It has been found impractical to use continuous chain stitch severing mechanisms and pneumatic suction systems to remove or control the connecting chain between seamed units on those sewing machines that are unable to form a continuous chain stitch. It has been found desirable to use one of several types of chain stitch severing mechanisms such as the one distributed by Clinton Industries, Inc. of Hackensack, New Jersey, Model Cutter CC115FCA.

It has been determined that the chain stitches on these particular machines have a tendency to pull out due primarily to the backfeed or reversal of thread travel from the feed dog and that improper seams are formed and faulty seam sewing occurs generally manifested by frequent jamming of the fabric under the presser foot on the throat plate. It is necessary in order to overcome this recurring problem that an operator must pull or apply considerable tension to the fabric in a direction opposite from the direction of fabric travel. In a fell seam, because of the four plies of fabric, the frictional resistence from one layer to another results in fabric displacement in the seam, and usually a distorted, non-uniform, or boardy seam is produced.

Therefore, it is an objective of this invention to provide an apparatus for a sewing machine in which a continuous chain stitch may be formed which eliminates stretching or tensioning by the machine operator to achieve a more uniformly satisfactory seam.

Another objective of this invention is to provide an apparatus for a standard industrial sewing machine in which a continuous chain stitch may be formed enabling an operator to chain-off one seam to another, with an appropriate spacing therebetween, without stopping the sewing machine or raising the presser foot to introduce another garment or section of a garment in which a seam is to be sewn.

Still another objective of this invention is to eliminate the necessity for a sewing machine operator to stretch the fabric and control the fabric tension as it is being fed to the sewing instrumentalities in order to obtain a satisfactory seam without binding and backfeeding from the feed dog opposed to the normal direction of fabric travel through the sewing machine by utilization of the advancing motion produced by the operation of the feed dog and feed dog mechanisms.

The apparatus of this invention includes a modified feed dog in which one or more rows of serrated teeth areforeshortened to cooperate with a modified throat plate and a pressure pad mounted on the presser foot in which the pressure pad is provided with one or more grooves or channels for guiding the path of travel of a continuous chain of stitches with the pressure pad also being provided with fabric gripping means to prevent thread backfeed. A throat plate is positioned between the feed dog and presser foot with the presser foot pressure pad cooperatively aligned with the foreshortened row or rows of serrated teeth on the feed dog to form a continuous chain stitch whereby a chain stitch severing mechanism of conventional type may be incorporated, if desirable.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevational view of an assembly of a presser foot, throat plate, and feed dog combination for continuous chain sewing embodying the invention for incorporation on a conventional industrial sewing machine;

FIG. 2 is an exploded perspective view of the feed dog and throat plate of FIG. 1; and

FIG. 3 is a bottom plan viewtaken substantially along the section line 33 of FIG. 1 of a fabric pressure pad mounted on the presser foot.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The present invention will be described within the environment of a standard Union Special Model 56900 sewing machine generally used for industrial sewing of garment seams including fell seams having a plurality of overlapping fabric plies. The conventional sewing machine feed mechanism is employed but the presser foot, feed dog and throat plate have been modified appropriately in order to produce a continuous chain stitch enabling an operator to chain-off successive units. Accordingly, only those details will be described which are deemed essential for a complete. full and clear understanding of this invention for use in combination with a two needle 401 chain stitch machine with full recognition that the improvement is applicable also to other machines of similar construction which will enable an operator to achieve the desired continuous chain stitch without intermittent operation.

The presser foot assembly is vertically elevatable and is shown in FIG. 1 in the operative down position for sewing with the fabric inlet guide member 12 being pivotally supported about the guide pin 14. A pair of laterally spaced-apart fabric guide members 16 depend downwardly from the presser foot assembly 10 to accommodate a fabric presure pad 18 therebetween which pressure pad also projects downwardly between and below the fabric guides 16. The leading edge 20 of pressure pad 18 is inclined upwardly to receive the leading end of a fabric (not shown) to be seamed from the discharge end of the pivotable fabric guide member 12 at the bottom thereof. The trailing section 22 of the pressure pad 18 is provided with a series of serrated fabric-engaging teeth 24 for preventing backward or reverse travel of the thread from its intended direction of travel from the fabric guide 12 in the direction of the pressure pad. The pressure pad 18, as shown in FIG. 3, is also provided preferably with two continuous chain stitch grooves or channels 26 corresponding to the number of needles (not shown) which form independent chains with their respective loopers (not shown) that are laterally spaced from each other in alignment with the needles mounted in the sewing machine. Enlarged chain stitch guide or entrance grooves 28 are provided in the pad 18 to assist in receiving or urging the chain of stitches in its directed path of travel in the groove or channel 26 as it moves to the serrated teeth 24 in pad 18. 1

The feed dog 30 is operatively connected to a conventional feeding mechanism and feed eccentrics (not shown) through the feed carrier link 32. The feed dog 30, as shown in FIG. 2, is provided with a series of laterally spaced-apart rows 34, 36, 38, and 42 of upwardly-projecting webs on each of which is a plurality of serrated fabric-engaging teeth 44 that are preferably uniformly spaced-apart on each web crest. The spacing of the teeth 44 above the presser foot may be conventional depending upon the fabrics used and the seams formed. The opening or cavity 46 in the feed dog 30 permits the penetration of one, two or three, or more needles depending upon the number of needles utilized in the particular sewing machine model. Web 34 is illustrated as having a greater height than the other webs 36 through 42, and is particularly suitable for sewing a fell scam in which there are four plies of fabric in order to engage and support a single fabric ply that is at a higher level or elevation than the folded four plies of fabric with the bottom ply of the fell seam being supported on the tops of the teeth 44 of the other webs. Usually the level at the crest of the teeth for webs 36 through 42 may be uniformly at the same height.

The trailing edges 48 and 50 of webs 36 and 40, respectively, are foreshortened in length by removing two or more teeth thereby providing an undercut relative to the adjacent webs and teeth in the same web for alignment and cooperation with the terminal portions 52-of the grooves 26in order to prevent chain stitch feedback.

The throat plate 54 is mounted on the sewing machine between the presser foot assembly 10 and the feed dog 30 in a conventional manner. A series of laterally-spaced elongated slots 56 is provided in the throat plate 54 through which the serrated teeth 44 on their respective webs may protrude upwardly, depending upon the desired setting for the particular fabric and seams being formed, to engage and advance the fabric being sewn in a directed path of travel in a conventional manner. Inserts 58 and 60 are provided in the throat plate 54 to cover the removed or undercut trailing edges or sections 48 and 50 in the webs 36 and 40 on the feed dog over which the thread and continuous chain may be guided after discharge from the chain stitch groove outlets 52 in the pressure pad 18 that is mounted on the pressure foot assembly 10.

In the embodiment illustrated, a two-needle machine is utilized. However, in the event a three-needle machine is employed, the web 38 may be similarly undercut and the appropriate matching slot in the throat plate 54 covered accordingly with inserts similar to the inserts 58 and 60. Should only a single-needle machine be employed, only one of the webs 36, 38 or 40 need be suitably undercut. It is not necessary to undercut either webs 34 or 42 as these will provide the requisite guiding and lateral support for the fabric as the seam is being sewn.

An operator is able to sew a more consistently uniform seam with no appreciable tension applied to the fabric as it is being fed to the sewing instrumentalities by utilizing the modified presser foot with the pressure pad 18, the improved feed dog 30, and the modified throat plate to form a continuous chain stitch.

I claim:

1. Apparatus for sewing machines to form a chain stitch continuously comprising: a presser foot, means on said presser foot for gripping a fabric being sewn traveling along a directed path of travel to prevent thread feedback, a feed dog cooperatively aligned with said presser foot and presser foot gripping means for advancing a fabric being sewn in a directed path of travel, a throat plate positioned between said presser foot and said feed dog, said feed dog having laterally spaced-apart fabric-engaging and upwardly projecting rows, each of said rows having a plurality of serrated teeth, at least one row having a trailing edge foreshortened in length relative to adjacent rows for cooperative alignment with said presser foot fabric gripping means, and said throat plate having means for cooperative alignment and covering the foreshortened row of serrated teeth whereby a continuous chain may be formed during sewing without seam stretching or tensioning.

2. Apparatus for sewing machines as claimed in claim 1, said presser foot having at least one chain guide groove therein for cooperatively receiving and guiding a chain stitch and seam along a directed path of travel to the gripping means on said presser foot.

3. Apparatus for sewing machines as claimed in claim 1, said feed dog having opposed sides with upwardly projecting rows, each row having a plurality of serrated teeth thereon, one of said rows being higher than said other row, and intermediate laterally spaced-apart rows between side rows, at least two of said intermediate rows having a lesser number of serrated teeth at the 5. Apparatus for sewing machines as claimed in claim 1, said presser foot gripping means having aligned chain guide grooves therein, a plurality of serrated teeth on said presser foot gripping means in the path of said chain guide grooves, said feed dog having a plurality of foreshortened rows of serrated teeth in the trailing edges thereof for cooperative alignment with said chain guide grooves in said presser foot fabric-gripping means. 

1. Apparatus for sewing machines to form a chain stitch continuously comprising: a presser foot, means on said presser foot for gripping a fabric being sewn traveling along a directed path of travel to prevent thread feedback, a feed dog cooperatively aligned with said presser foot and presser foot gripping means for advancing a fabric being sewn in a directed path of travel, a throat plate positioned between said presser foot and said feed dog, said feed dog having laterally spacedapart fabric-engaging and upwardly projecting rows, each of said rows having a plurality of serrated teeth, at least one row having a trailing edge foreshortened in length relative to adjacent rows for cooperative alignment with said presser foot fabric gripping means, and said throat plate having means for cooperative alignment and covering the foreshortened row of serrated teeth whereby a continuous chain may be formed during sewing without seam stretching or tensioning.
 2. Apparatus for sewing machines as claimed in claim 1, said presser foot having at least one chain guide groove therein for cooperatively receiving and guiding a chain stitch and seam along a directed path of travel to the gripping means on said presser foot.
 3. Apparatus for sewing machines as claimed in claim 1, said feed dog having opposed sides with upwardly projecting rows, each row having a plurality of serrated teeth thereon, one of said rows being higher than said other row, and intermediate laterally spaced-apart rows between side rows, at least two of said intermediate rows having a lesser number of serrated teeth at the trailing edges thereof, said throat plate having means covering the foreshortened rows of serrated teeth.
 4. Apparatus for sewing machines as claimed in claim 1, said presser foot gripping means having a pair of spaced-apart chain stitch-receiving grooves therein in alignment with needles on the sewing machine for guiding said chain stitches in a directed path of travel to said gripping means, said gripping means including a series of serrated teeth depending downwardly for engaging a chain stitch and for maintaining alignment of the chain stitches discharged from said grooves.
 5. Apparatus for sewing machines as claimed in claim 1, said presser foot gripping means having aligned chain guide grooves therein, a plurality of serrated teeth on said presser foot gripping means in the path of said chain guide grooves, said feed dog having a plurality of foreshortened rows of serrated teeth in the trailing edges thereof for cooperative alignment with said chain guide grooves in said presser foot fabric-gripping means. 